Experiments carried out recently in this laboratory have shown that an estrogenic hormone will reversibly inhibit the maturation of pig oocytes in vitro, and that progesterone will overcome the inhibition. It has also been demonstrated that estradiol-17 beta associates with pig oocytes during culture, indicating the possible existence of steroid receptors in oocytes. The proposed project is designed to investigate the interaction between steroid hormones and mammalian oocytes in vitro, and to examine the effects of such interactions at the cellular, chromosomal and molecular levels. To examine these interactions a culture system, developed in this laboratory will be used as a bioassay for oocyte maturation in vitro. Varied steroid combinations will be tested for their influence on the maturation of intact (with granulosa cells) and denuded (granulosa cells removed) pig oocytes. Cultured oocytes will be examined by two methods. Groups of oocytes will be air-dried for examination of nuclear maturation and the incidence of chromosomal abnormalities. Other oocytes will be subjected to analysis of protein synthetic patterns by two-dimensional polyacrylamide-gel electrophoresis with autoradiography.